import java.util.List;

public class LinkedList implements Ilist{

    static class ListNode{
        public int val;
        public ListNode prev;
        public ListNode next;

        public ListNode(int val) {
            this.val = val;
        }
    }

    public ListNode head;
    public ListNode last;


    @Override
    public void addFirst(int data) {
        ListNode node = new ListNode(data);
        if(head == null) {
            head = last = node;
        }else{
            node.next = head;
            head.prev = node;
            head = node;
        }
    }

    @Override
    public void addLast(int data) {
        ListNode node = new ListNode(data);
        if(head == null) {
            head = last = node;
        }else{
            node.prev = last;
            last.next = node;
            last = node;
        }
    }

    @Override
    public void addIndex(int index, int data) {
        int count = size();
        if(index < 0 || index > count){
            return;
        }
        if(index == 0){
            addFirst(data);
            return;
        }
        if(index == count){
            addLast(data);
            return;
        }

        ListNode cur = head;
        while(index != 0) {
            cur = cur.next;
            index--;
        }

        ListNode node = new ListNode(data);

        node.next = cur;
        cur.prev.next = node;
        node.prev = cur.prev;
        cur.prev = node;

    }

    @Override
    public boolean contains(int key) {
        ListNode cur = head;
        while (cur.next != null){
            cur = cur.next;
            if(cur.val == key){
                return true;
            }
        }
        return false;
    }

    @Override
    public void remove(int key) {
        /*ListNode cur = head;
        while (cur.next != null){
            if(cur.val == key){
                if(cur == head){
                    head = head.next;
                    if(head != null){
                        head.prev = null;
                    }
                }else {
                    cur.prev.next = cur.next;
                    if(cur.next == null){
                        last = last.prev;
                    }else {
                        cur.next.prev = cur.prev;
                    }
                }
                return;
            }
            cur = cur.next;
        }*/


        /**/if(head.val == key){
            head = head.next;
            if(head != null){
                head.prev = null;
            }
            return;
        }
        ListNode cur = head;
        while (cur.next != null){
            if(cur.val == key){
                cur.prev.next = cur.next;
                cur.next.prev = cur.prev;
                return;
            }
            if(size() == key){
                cur.prev.next = null;
                last = last.prev;
                return;
            }
            cur = cur.next;
        }
    }

    @Override
    public void removeAllKey(int key) {
        /*ListNode cur = head;
        while (cur.next != null){
            if(cur.val == key){
                if(cur == head){
                    head = head.next;
                    if(head != null){
                        head.prev = null;
                    }
                }else {
                    cur.prev.next = cur.next;
                    if(cur.next == null){
                        last = last.prev;
                    }else {
                        cur.next.prev = cur.prev;
                    }
                }
            }
            cur = cur.next;
        }*/
        ListNode cur = head;
        while (cur.next != null){
            if(cur.val == key){
                remove(key);
            }
            cur = cur.next;
        }/**/
    }

    @Override
    public int size() {
        ListNode cur = head;
        int count = 0;
        while (cur != null){
            cur = cur.next;
            count++;
        }
        return count;
    }

    @Override
    public void display() {
        ListNode cur = head;
        while (cur != null){
            System.out.print(cur.val + " ");
            cur = cur.next;
        }
        System.out.println();
    }

    @Override
    public void clear() {
        ListNode cur = head;
        while (cur != null){
            ListNode curN = cur.next;
            cur.next = null;
            cur.prev = null;
            cur = curN;
        }
        head = last = null;
    }
}
